Reduced Effectiveness of Emergency Contraception in Women with Increased BMI

to the editor: Thank you for the article discussing the various methods of emergency contraception. We were surprised to find that the authors reported insufficient evidence to recommend against the use of emergency contraception in women with a body mass index (BMI) greater than 30 kg per m2.

A report using data from randomized trials examined the risk factors for failure of levonorgestrel and ulipristal (Ella) after unprotected intercourse.1 The authors found that the risk of pregnancy increased for women using levonorgestrel who had a BMI greater than 25 kg per m2. Pregnancy rates for women using levonorgestrel who had a BMI greater than 26 kg per m2 were essentially the same as those in women who did not use any emergency contraception. The effectiveness of ulipristal also appears to decrease with increasing BMI, although at a much slower rate. This information is crucial considering the number of women in this country who are overweight or obese, and the high cost of emergency contraceptives.

in reply: We agree that recent data suggest decreased effectiveness for emergency contraception in women who are obese or overweight.1 Two randomized trials found that the pregnancy rate was 5.8% in this population after using levonorgestrel, compared with a pregnancy rate of 5.6% in the absence of emergency contraception.1 Before concluding that emergency contraception is ineffective in women with a BMI greater than 30 kg per m2, subsequent studies should look specifically at this population and control for factors such as routine contraception use, timing of intercourse, and multiple acts of intercourse in the same menstrual cycle.

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